1. Field of the Invention
This invention relates to novel fiber-forming copolyamides containing from 0.5 to 7.5 percent by weight of phosphorus as an integral part of their polymer chains, wherein the phosphorus is present in chain-extending radicals of the formula ##STR1## WHERE R represents alkyl having from 1 to 4 carbon atoms and x and y each represent the integer 2 or 3. Fibers prepared from the copolyamides of the invention have permanent antistatic, moisture transport and flame-resistant properties. The term fiber as used herein includes continuous filament yarns, monofilaments, tows and spinnable staple.
2. Description of the Prior Art
Polyamide fibers such as fibers of polyhexamethylene adipamide (nylon 66) have exceptional strength and durability and are widely used in textile applications such as in carpets, apparel and upholstery. These fibers, however, lack adequate antistatic, moisture transport and moisture regain (i.e., comfort) and flame-resistant properties for certain textile fiber applications. Therefore, when polyamide fibers having these latter properties are needed, appropriate additives are used. Melt additives are normally preferred over surface coatings provided by additives since the latter are easily removed from yarns and also tend to impart a hard or harsh hand thereto. Conventionally, a melt additive or combination of melt additives is dispersed into a polyamide by mixing one or more melt additives with molten polyamide prior to fiber formation. Wax-like materials such as low molecular weight polymers comprising poly(alkylene ether) moieties, for example, the polyether waxes disclosed in U.S. Pat. Nos. 3,388,104 and 3,848,023, are very effective melt additives for use in improving the antistatic and moisture transport properties of polyamide fibers. Unfortunately, polyamide fibers which contain sufficient amounts of these wax-like materials to be adequately antistatic tend to lack desirable flame resistance for use in certain applications such as in shag carpets. While there are a few halogen-containing flame retardants such as octabromodiphenyl which might possibly be used as melt additives with the wax-containing polyamide fibers at a concentration of 6-10% o.w.p. (on weight of polymer) to improve their flame resistance, these flame retardants generally have poor dye light fastness and therefore are not suitable for most textile fiber applications. Additionally, loading fibers with large amounts of melt additives of any type is undesirable. Not only are melt additives costly and require additional processing steps, but they give rise to spinning difficulties and also tend to reduce the strength of the resulting fibers. Moreover, melt additives tend to exude from polyamide fibers and therefore the properties imparted to the fibers by their use are not permanent.
Polyamides containing phosphorus as an integral part of their polymer chains are described in the prior art, for example, U.S. Pat. No. 2,646,420 discloses high shrinkage fibers of polyamides containing recurring ##STR2## radicals and British Pat. No. 1,012,009 discloses low melting films of a polyamide containing recurring ##STR3## radicals. These fibers and films reportedly are flame-resistant. However, neither have good antistatic or moisture regain transport properties and, therefore, melt additives would nevertheless be needed for their use in certain applications. U.S. Pat. No. 3,108,991 discloses water-soluble, flame-resistant homopolyamides containing, for example, recurring ##STR4## radicals, where R is a lower alkyl. These homopolyamides are not capable of being made into useful fibers. However, even if they could be made fiber-forming, their water-solubility would render them completely unsatisfactory for use in apparel, carpet and upholstery application.
It will be apparent to those skilled in the art that it would be highly desirable to provide polyamides which can, without the use of additives, be made into useful textile fibers having in combination permanent antistatic, moisture transport, moisture regain, and flame-resistant properties.
It is therefore an object of the present invention to provide such polyamides and also to provide useful fibers made therefrom.